Applicant""s invention relates to a method to provide failover protection to a data storage and retrieval system in the event of the failure of a robotic accessor moveably disposed therein.
Automated media storage libraries are known for providing cost effective access to large quantities of stored media. Generally, media storage libraries include a large number of storage slots on which are stored portable data storage media. One (or more) accessors typically access the data storage media from the storage slots and deliver the accessed media to a data storage device for reading and/or writing information on the accessed media. Suitable electronics operate the accessor(s) and operate the data storage device(s) to provide information to, and/or to receive information from, one or more host computers.
In certain embodiments, the storage slots are arranged in a planar orthogonal arrangement forming a xe2x80x9cwallxe2x80x9d of storage slots for holding data storage media. The plane may be a flat plane, or may be a cylindrical plane. In certain embodiments, two xe2x80x9cwallsxe2x80x9d of storage slots may be provided on either side of the one or more accessors.
A number of different companies manufacture automated media storage libraries today, each model displaying various different features. One example is the IBM 3584 Media Storage Library. Some of the automated media storage libraries have dual or multiple accessors to provide a level of redundancy and to enhance performance.
Applicants"" invention includes an accessor moveably disposed in Applicant""s data storage and retrieval system, where that data storage and retrieval system is capable of communicating with one or more host computers. Applicant""s accessor includes an accessor controller containing, among other things, a work queue comprising a computer database which includes information regarding one or more work requests made by one or more host computers, or by the system operator, or by system""s I/O controller. Each accessor controller creates a work entry corresponding to each work request received. Each such work entry includes information which includes, for example, the time the work request was received, the operations required to complete that work request, the accessor handling the work request, and the status of that work request.
Applicant""s invention further includes a data storage and retrieval system which comprises at least two of Applicant""s accessors. Applicants"" data storage and retrieval system further includes a data and control network that interconnects, inter alia, each of Applicants"" accessors moveably disposed in Applicants"" data storage and retrieval system.
Applicants"" invention further includes a method to provide failover protection to Applicants"" data storage and retrieval system in the event of a failure of one of Applicant""s accessors, where that data storage and retrieval system includes a data and control network, one or more portable data storage media, and two or more of Applicant""s accessors. Applicant""s method includes the steps of receiving a work request from a host computer, creating a pending work entry comprising that move request, communicating notification by one of the accessors, i.e. a first accessor, to the other accessors, i.e. the one or more remaining accessors, that the first accessor is handling the pending work entry, acknowledging that notification by the remaining accessors, initiating that pending work entry, reporting the status of the pending work entry, and updating the work queue disposed in each accessor to indicate the completion of the work entry.
Applicants"" invention further includes a data storage and retrieval system which includes a computer useable medium having computer readable program code disposed therein for implementing Applicant""s method to provide failover protection to Applicant""s data storage and retrieval system in the event of a failure of one of Applicant""s accessors.